1. Field of the Invention
The present invention relates generally to backlight modules, and more particularly to a polarization splitting backlight module for converting non-polarized light beams into light beams of a single polarization state.
2. Description of the Related Art
With the advent of the information technology (IT) age, there is an increasing demand for high-quality electro-optical displays, such as LCDs. Higher quality imaging requires the more efficient utilization of light sources. Conventionally, for obtaining single-polarized light beam output from a LCD backlight module, a polarization plate is arranged near the light source to inhibit the passage of certain polarized light beams, whereby the polarized light beams which are not parallel are prevented from being transmitted. In practice, the resultant light beams of a single polarization state are less than half of those of the original light source in terms of illuminance.
With reference to FIG. 1, a conventional liquid crystal display comprises a non-polarized light source 30, a diffuser 20, a polarization plate 14 and a liquid crystal component 50. Light beams emitted from the non-polarized light source 30 are introduced into the diffuser 20, and are screened by the polarization plate 14 so as to output light beams of a specific polarization state to be utilized by the liquid crystal component 50. The intensity of the resultant light beams will be reduced over 50% and will be less than half of the intensity of the original light beam due to the screening effect of the polarization plate 14. Since the optical energy loss between the resultant and original light beams is considerable, the power consumption of a system using such a module is very significant, thereby limiting the quality of the image display.
In view of the above problems, the principal object of the present invention is to provide a polarization splitting backlight module for converting light beams into a single polarization state, which reduces the optical loss in light beam output, is suitable for mass production, and decreases manufacturing costs.
Another object of the present invention is to provide a polarization splitting backlight module, which is easily integrated with conventional light guides and achieves high-quality polarization splitting.
To achieve the first object, the present invention provides a polarization splitting backlight module for converting light beams into a single polarization state, comprising an under plate having an upper surface and a ridged lower surface; a phase retardation film of high reflectivity, disposed on the ridged lower surface of the under plate; a substrate having a lower surface, substantially complementary to the upper surface of the under plate and facing therewith, and a ridged upper surface; a light source located at the lateral side of the substrate and the under plate for emitting a plurality of light beams; a scattering structure disposed between the substrate and the upper surface of the under plate for altering the polarization state and the travelling direction of the light beams; an upper cover having a ridged lower surface, substantially complementary to the ridged upper surface of the substrate and facing therewith, and an upper surface; and a thin film disposed between the upper cover and the substrate, having an index of refraction different from that of the substrate.
The present invention further provides a polarization splitting backlight module, comprises a substrate having a ridged upper surface and a ridged lower surface, a scattering structure disposed on the ridged lower surface of the substrate, a phase retardation film of high reflectivity disposed under the scattering structure, an upper cover having a ridged lower surface and an upper surface, and a light source located at the lateral side of the substrate. Furthermore, the ridged lower surface of the substrate in the above construction may be modified as a flat surface without affecting the polarization splitting effect of the backlight module.
In order to enhance the optical performance, the ridge pitch of each ridged surface may be constant or not so as to increase the design freedom. Moreover, in order to increase the efficiency for altering the polarization states, the phase retardation reflective film is utilized. In addition, four lateral side-surfaces of the polarization splitting backlight module may be optionally provided with reflective films, so as to confine the light beams within the backlight module and thereby increasing the transmission efficiency of the light beams through the upper surface of the upper cover.
To achieve the second object, the present invention provides a polarization splitting backlight module for converting light beams into a single polarization state, comprising an under plate having an upper surface and a ridged lower surface; a phase retardation film of high reflectivity, disposed on the ridged lower surface of the under plate; a substrate having a lower surface, substantially complementary to the upper surface of the under plate and facing therewith, and an upper surface; an upper cover film having a lower surface, substantially complementary to the upper surface of the substrate and facing therewith, and a ridged upper surface; a light source located at the lateral side of the substrate and the under plate for emitting a plurality of light beams; a scattering structure disposed between the substrate and the upper surface of the under plate for altering the polarization state and the travelling direction of the light beams; an upper cover having a ridged lower surface, substantially complementary to the ridged upper surface of the upper cover film and facing therewith, and an upper surface; and a thin film disposed between the upper cover and the upper cover film.
With this construction, the polarization splitting backlight module can be easily integrated with a conventional liquid crystal display backlight module by attaching the lower surface of the upper cover film and the upper surface of the substrate to the upper side and lower side of the diffuser of the conventional backlight module respectively.
Additional advantages, objects and features of the present invention will become more apparent from the description which follows.